Greases prepared by alkali fusion of fatty materials



sw m u Ame it The present invention relates to new and improved lubricating greasesand to. a new process of preparingthe same. More particularly, the invention pertains to a method of manufiacturing new and improved lubricating greases of high dropping poi-ntand-soft consistency over a wide temperature range and to greasesproduced by this method.

In its broadest aspect, the invention provides for the preseason of greases in whichthe thickenin agent is a iniiitti're or fatty acid soap obtained by sapo'ni-fic'ation and cr me product obtained by heating g'lyce'ri'ne at high temperature in the presence of alkali. I-Iigh tempera- 't'ure greases of *ei'r'cel l'en't "quality may be produced in this "manner.

Pi'ior to the present invention, soap-thickened greases 6f d'sii ablehardfn'ess characteristics and high melting "-iir 'ctfoppiiig parsere,greases-matting aboveahout 400 F. an having {a smash soft consistency ever a wide te perature range, i; -e., between about 200 and 100* F5, have been known; Thes'e greases have been prepa'r d' B'y 'the sapohification arrap'e'seed oil with *an-excess of alkali Whileheating toa temperaturebetween 48'6" and 520 F. 'in a lubricating oil vehicle containing a entail atho'unt-of sodium sulfona'te as described-in "S. I atent Ne. 226591.

The desirable combination of excellent qualities of of the soap. Rapeseed oil and the Brassidieramily-are the only known coiniiiercia'l source's-tor these materials. Ei' iicic "acid is present in "fish 'oil but cannot be readily separated 'th ro'm. Actually it has not beenpossible heretofore to prepare soap thilfied greases liayi'ng sirniiaripreperries from other glyceride-typefats or "o'ils nor from the corresponding fatty acids as such. Even attempts of preparing similar greases by 'saponifyingr syn- "ihtic *coinpesrts approximatin rapeseed oil have failed.

More specifically, prior to the present invention no process was '"kn'own'by which such 'glyceri'des as 'tallow, other fats 'rich in stearin, or saturated or hydrogenated fats and oils or unsaturated oils other than rapeseed cil -"could be c'dnv'e'rted into desirable high temperature greases. While grease products having high melting ipoi'n-ts have been obtained from these-raw materials,

the products are extremely hard and dry and unsuitable for ball or'roller bearings requiring soft unctuousgreases.

This situation is unsatisfactory particularly whenever there eiris'ts "a shortage 'dtrapeseedbil as it actually occurred during war time. Etiorts to produce 'a. good 'iitiality high temperature grease from such rapeseed oil substitutes as mixturesof 50% oleic acid and-50% 'e'ru'cic lt isyth'erfore, an important objectofthepres'ent inventiontdprovfde soap-thickened,gocii'qualityhigh tem- 2,790,769 Patented Apr. 30, 1,957

ice

seed oil. Other objects and, advantages will appear vfrom the :following: description of the invention. i

It has now been found that :glyceride-type fats and oils and mixtures approximating the composition ofsuch fats and oils may be used quite generally inplaceaof rapeseed oil for the production of high temperature greases of excellent quality provided a large ex cessuof aikaii over the amount required for sapon-ification of the giycerides or neutralization of thecfatty :acid .is employed, and saponification or neutralization properisfo'llowed' by heating of the-reaction mixture' to such temperatures substantially exceeding 520 F. as are conducive-to alkali fusion of the glycerine with accompanying evolution of hydrogen. Whilethereaction mechanism is not fully understood, it may be postulated (that, inthe second high temperature stage, the :glycerine split off duringthe-carlier 'saponificationv stage or otherwise introduced into the :reaction mixture is dehydrated to form acroleinor a dimer thereof. Upon continued heating the acrolein or its dimer isconverted into a salt by alkali .fusion either directly or via the-Cannizzaro reaction. Alkali fusioniof the alcohol formed in theCanniZzaro reaction v rnayralso occur. Reactions of the following type may be involved:

"The econd; i-" f ieh sh tempe tu re mer in v Reactions 2-5. v

" c rry n out the P es ntion, the amou t r Prefe ably at lea t w e ha eq ired 1 pl'e'tely to 's'ap'o fythelfatsor neutralize the fatty acid us d The 8 st e o n n o cons s i lnwly heatingth "reaction mixture until sapon'ifica'tion or acid "neutralizz' on 'is completed. This is satisfactorily accomplis jdat atemjperat1 re'below 400".F. Thereafter, h at i s o nu at tempe a ure inlthe' r n o ab saw-570 F. u t o m g c ed by lu iq ceases. It isgpa rticular'ly tdbe noted thatthis second re ction, d e riot nitiat elo th s ng n emp oying suitablestarting materials 'otherlhan rapeseed oil.

Withinihis range, 'theitemperatures required in the second stagearefhi gher .forsaturated or hydrogenated fats and fatty acids 'th n- 'for' unsaturated saponifiablema- "terials. lnthe case ofthe'former, alkaliliusionaccomjpanied'by gas eyolution andtoarning may begin at about perature greases based on raw materials other tha'nrarie 0 an s op zi bou '5 Q" mpa t: abou nd"5 0' 1 h cor sp din empe atur i the lease of unsaturated'sap'onifiable'materials. "Onfthe other hafid,"when rapeseedoil' isused in accordance with theknown'procedure, saponification iscompleted atabout "300 350" "and 1 gas evolution and foaming begin at abeue tso Fame-eliminate acabQut SOO F.

Soap-forming base materials useful for the purposes of -the"preseht invention-arequiteagenerally saturated or unand should not exceed about twice that amount.

tion.

Regarding the coolingstage, it is'noted that cooling saturated or hydrogenated naturally occurring glyceridetype fats and oils of animal or vegetable nature, such as tallow, hog fat, etc., which begin to react with alkali to produce hydrogen at temperatures above about 520 F., as well as mixtures of saturated and/or unsaturated high molecular weight fatty acids with glycerine. Mixtures of glycerides with fatty acids and glycerine can, of course, be used. Of the saturated acids, those containing 12-30 carbon atoms, such as lauric or myristic, and preferably palmitic, stearic, behenic acids are operable. The preferred unsaturated acids are those containing at least 18 and up to about 22 carbon atoms. However, the acids containing conjugated bonds such as the acids of oiticica, tung and similar drying oils should be used if at all in small quantities since they tend to polymerize giving undesirable properties. When mixtures of fatty acids and glycerine are used, the propor tion of glycerine is preferably that corresponding to or approximating the glyceride of the fatty acid involved In the latter case, correspondingly larger amounts of alkali should be used.

As in the case of greases based on rapeseed oil, the addition of small amounts, say, about A to about 2% based on the finished grease, of an oil soluble sulfonic 'compound derived from petroleum should be added to increase the soft and unctuous quality of the grease and its temperature stability. A petroleum sulfonic acid or an alkali metal soap thereof may be used for this purpose. Other conventional grease additives, such as antioxidants, especially amino compounds, dispersauts, extreme pressure agents containing sulfur, etc., may be added.

Regarding suitable lubricating oil bases, mineral oils or unsaponifiable synthetic oils should be used until alkali fusion is completed. For example, a non-paraflinic mineral oil may be employed in this stage of the process. After fusion and after recrystallization of the soap at a temperature below 300 F., any desired type of lubricating oil including ester-type synthetic oils may be added.

Greases, in accordance with the invention, quite generally, may be prepared as follows. The glyceride or a mixture of high molecular weight fatty acids with glycerine is charged together with about 50% of the total lubricating oil requirement to a heated grease kettle and warmed to about 130-150 F. Alkali metal hydroxide, preferably sodium hydroxide is added in an amount at least twice, but preferably greater than twice, as much as that required to saponify the fat or acid. An excess of 100-125% over saponification requirements should be used, preferably in the form of a 50% aqueous solution of NaOH. The temperature is then raised to about 350-400 F. and the balance of the lubricating oil is added. Heating is continued to melt the mass completely and beyond this point until foaming begins, becoming appreciable at temperatures of about 530-550 F. Foaming is usually violent enough to require top stirring which prevents overflowing. The temperature is further raised until foaming commences to recede, which takes place after a temperature rise of about F. This temperature which usually falls between about 550 and 570 F. is maintained for about 20-40 minutes until foaming has ceased.

The grease may then be allowed to cool to about 300-330 F. whereupon at least a portion of the remaining excess alkali may be neutralized by the addition of fat or fatty acid. The grease should have a free alkalinity of less than 1.0%. Thereafter, further quantities of lubricating oil may be added to adjust the grease consistency to the desired degree. Concentrations of 15-30 wt. percent, based on the finished grease, of total soaptype thickener are suitable for the purposes of the inventimes of about 8-22 hours have been used heretofore when working with rapeseed oil. Similar cooling times may be employed in the present process. It has been found, however, that the cooling time may be shortened to as little as 610 hours for the temperature interval from about 570 F. to about 200 F. when sufficient acid is added during the cooling process completely to neutralize any excess free alkalinity remaining after fusion and to have even a slight excess of acid in the finished grease, .as it is disclosed andclaimed more broadly in the copending Morway application Serial No. 289,898, filed May 24, 1952, now abandoned, and assigned to the same interests. In addition to substantial savings in processing equipment due to the shortened cooling times, the greases so prepared have satisfactory lubrication life without any loss in high temperature quality.

Greases obtained in accordance with the present invention have dropping points substantially in excess of 400 F. They have a soft, unctuous consistency at temperatures above 20 F. and retain the same over a wide temperature range.

The invention will be further illustrated by the following specific examples which represent preferred modifications of the invention.

EXAMPLE I About 20 parts by weight of hydrogenated tallow and 36 parts by weight of low cold test naphthenic type mineral oil having a viscosity of S. S. U. at 210 F. (oil A) were charged to a fire heated grease kettle and warmed to F. About 6 parts by weight of sodium hydroxide in a 50% aqueous solution was charged, the quantity of NaOH being more than twice that required to saponify the fat. The temperature was then raised to 400 F. where an additional 36 parts by weight of a low cold test naphthenic type mineral oil having a viscosity of 40 S. S. U. at 210 F. (oil B) was added. Heating was continued. At 500 F., the grease was completely molten with only slight foam formation. At 550 F. foaming became more evident and at 560 F. the kettle was completely filled with foam requiring top stirring to retain the product in the kettle. At 570 F. the foaming commenced to recede. The batch was held between 550 and 570 F. for /2 hour.

A sample taken at 500 F. had a dropping point of 457 F. while a sample taken at 570 F. had a dropping point of 482 F.

The grease was cooled .while stirring to 330 F. when sufficient hydrogenated tallow was added to neutralize /3 of the remaining excess caustic. A sufficient amount of oil B was added to hold the soap concentration at 20% by weight. The cold grease had the following properties.

Appearance--excellent, smooth, uniform short fiber product Water solubility5% loss in AN--G-15 water washing test 1 Method described in AN-G-15 Government specification.

The gas evolved during fusion had the following composition:

Percent Hydrogen 81.0 1 Carbon dioxide--- 2.3 Saturated hydrocarbons 14.4 Unsaturated hydrocarbons 2.3

This analysis confirms the evolution of hydrogen during the fusion process and thus tends to substantiate re- 6 seed oil, a grease was prepared essentially asin Experiment A fromthe following ingredients:

. Parts Ingredients :bv

Weight Oleic Acid- 1 0.00

Hydrofol A. B. Acids -10.

Glycerine v v p 2.00

1 Sodium Hydr e 4.75

50% Solution of Sodium Petroieurn 'Sulfonate in Mineral Oil. 1.00

Phenyl-a-Naphthylamine Oxidation Inhibitor 1.00 Condensation Product of Salieylal and'Ethyl e Dia ne,

, Oxidation Inhibitor v .0. 50

Blend of Oil A and Oil B, Having Viscosity o'f50'SfSJUCat This grease was prepared essentially as described in Example I with the exception that after addition of the second batch of mineral oil, heating was continued to 530 F. The temperature was held at this level until foaming had ceased. After cooling the grease hadthe following properties:

Penetrations, 77 F., mm./'1'0:

Unworked Too soft. Worked, '60'st'rokes Too'soft. Worked, 100,000 strokes Fluid. After high shear-type homogenization at 4,000

p. s. i 227. Norman-Holfman, 'hrs.'to 5 p. -s. i., drop in oxygen pressure (after homogenization) "170. {Spindle liife,hou'rs (after homogenization) 1507. Percent free alkalinity as "NaOH '01'28. Dropping point, F 465.

It will be seen that this grease has a highly satisfactory dropping point and may be homogenized to acquire satisfactory penetration characteristics.

EXAMPLE III The advantages of the present invention over prior art types of procedures are best illustrated by the following experiments.

Experiment A A grease was prepared by the process of U. S. Patent No. 2,265,791 from the following ingredients:

The rapeseed oil and /2 of the mineral oil was charged to a fire heated grease kettle and warmed to 150 F. while agitating. The sodium sulfonate-niineral oil solution was added followed by a 40% aqueous solution of the sodium hydroxide. The temperature was raised and the soap formed was dehydrated at 300-350 F. At this temperature the balance of the mineral oil was slowly added while continuing to raise the temperature. At 425 F. a second reaction initiated as indicated by foam formation. This foaming continued while the temperature was raised to 500 F. At this temperature foaming ceased, heating was discontinued and the grease cooled while agitating to 275 F. when the inhibitors were added. The grease was further cooled to 200 F. and filtered while drawing in packages.

Experiment B In an attempt to prepare a high quality grease by the prior art process but using ingredients other than rape- 1 Hydroiol A. B. acids composition, percent:

.At'temperatures'up "to 500 F. at which'the experiment was terminated no secondary reaction involving foaming or gas evolution'ha'd occurred.

Experiment C The same ingredients as in Experiment B were 'used and treated as in Experiments A and .B except that heating was continuedabove '500"F. 'At"53'0 .'F., the second reaction initiated. .It was'eomple'tedat 550 F. This grease'wa'sthen finished as in Experiments A andB.

These three greases were tested with the results tabulated below.

Experiments Top Manufacturing Temperature, F. 500 500 550 2nd Reaction Occurs, F 425 None 530 2nd Reaction Terminates, F 500 550 Penetrations, 77 F. mm./l0:

Unworked 260 205 Worked 60 strokes"--. 285 290 285 Worked 100,000 strokes 360 fluid 376 Dropping Point, F 500 36 520+ Water Solubility Soluble Percent Free Alkalinity as NaOH 0. 22 l. 0. 17 Norma Hofiman Bomb Oxidation Test Hrs.

to 5 p. s. i. Drop in Oxygen Pressure:

Uninhibited 24 Tnhihirpd Homogenization: 1 Worked Penetration 186 1 Fine hole worker plate 270-Mo" holes. p sUiltimate hardness after high shear type homogenization at 4,000

The superiority of the grease in Experiment C which corresponds to the present invention is manifest. This grease has the highest dropping point and has good penetration and oxidation characteristics.

The present invention is not limited to any theory of the process of grease manufacture nor to the specific examples set forth above. The relative proportions of the grease constituents may be varied within the limits indicated to obtain greases of different consistency and varying characteristics.

In the following claims, the terms saponifying, saponifiable and saponification refer to the formation of soaps by an alkali treatment of fats, oils and/or fatty acids.

What is claimed is:

1. The process of preparing lubricating greases adapted for lubrication at high temperatures which comprises saponifying in a mineral lubricating oil in grease-making proportions a saponifiable material selected from the group consisting of (1) mixtures consisting of saturated high molecular weight fatty acids and glycerine, (2) mixtures consisting of unsaturated high molecular weight fatty acids and glycerine, said glycerine being present in an amount corresponding to that present in the glycerides of said fatty acids and (3) glycerides of high molecular weight fatty acids, with an amount of sodium hydroxide which is about 100 to 125% more than that required to saponify said material, heating the resulting mixture to complete the saponification of the fatty acids, continuing heating at a temperature of about 530 to 570 F. until hydrogen gas evolution recedes, and then cooling to obtain said lubricating grease.

2. The process of claim 1 wherein said saponification is carried out in the presence of a small amount of an oilsoluble sulfonic compound derived from petroleum.

3. The process of claim 1 wherein said high molecular weight fatty acids have from about 12 to 30 carbon atoms per molecule. a

4. The process of preparing lubricating greases adapted for lubrication at high temperatures and containing a major proportion of mineral lubricating oil, which comprises charging to a reaction vessel about 50% of said 7 proportion of lubricating oil, and a minor grease-making proportion of a soap-forming material consisting of a mixture of high molecular weight fatty acids having about 12 to 30 carbon atoms per molecule with an amount of glycerine corresponding to that present in the glycerides of said acids, heating the resulting mixture to a temperature of about 130 to 150 F., adding to said heated mixture sodium hydroxide in an amount of about 100 to perature of about 530? to 550 F. at which foaming and hydrogen evolution begins, further heating to a level between about 550 to 570 F. at which foaming commences to recede, maintaining said temperature level from about 20 to minutes until foaming and hydrogen evolution has substantially ceased, and then cooling to obtain said lubricating grease composition.

5. The process of claim 4 wherein said soap-forming material comprises a free fatty acid selected from the group consisting of oleic, myristic, palmitic, stearic, arachidic, behenic and myristoleic acids.

References Cited in the file of this patent UNITED STATES PATENTS 2,265,791 Zimmer et al Dec. 9, 1941 2,360,631- Zimmer et al Oct. 17, 1944 2,413,121 Swenson Dec. 24, 1946 2,445,935 Bondi July 27, 1948 2,449,312 Murray et a1 Sept. 14, 1948 2,468,098 Morway et al. Apr. 26, 1949 2,468,099 Morway Apr. 26, 1949 2,487,080 Swenson Nov. 8, 1949 2,487,081 Swenson Nov. 8, 1949 2,495,651 Butcosk Ian. 24, 1950 2,503,969 Rudel et a1 Apr. 11, 1950 2,514,286 Morway July 4, 1950 2,545,126 Whitney Mar. 13, 1951 2,583,435 Morway Jan. 22, 1952 2,595,161 Morway Apr. 29, 1952 

1. THE PROCESS OF PREPARING LUBRICATING GREASES ADAPTED FOR LUBRICATION AT HIGH TEMPERATURES WHICH COMPRISES SAPONIFYING IN A MINERAL LUBRICATING OIL IN GREASE-MAKING PROPORTIONS A SAPONIFIABLE MATERIAL SELECTED FROM THE GROUP CONSISTING OF (1) MIXTURES CONSISTING OF SATURATED HIGH MOLECULAR WEIGHT FATTY ACIDS AND GLYCERINE, (2) MIXTURES CONSISTING OF UNSATURATED HIGH MOLECULAR WEIGHT FATTY ACIDS AND GLYCERINE, SAID GLYCERINE BEING PRESENT IN AN AMOUNT CORRESPONDING TO THAT PRESENT IN THE GLYCERIDES OF SAID FATTY ACIDS AND (3) GLYCERIDES OF HIGH MOLECULAR WEIGHT FATTY ACIDS, WITH AN AMOUNT OF SODIUM HYDROXIDE WHICH IS ABOUT 100 TO 125% MORE THAN THAT REQUIRED TO SAPONIFY SAID MATERIAL, HEATING THE RESULTING MIXTURE TO COMPLETE THE SAPONIFICATION OF THE FATTY ACIDS, CONTINUING HEATING AT A TEMPERATURE OF ABOUT 530* TO 570*F. UNTIL HYDROGEN GAS EVOLUTION RECEDES, AND THEN COOLING TO OBTAIN SAID LUBRICATING GREASE. 